The present disclosure relates generally to building management systems and associated devices. More particularly, the present disclosure relates to a controller and actuator with valve control capabilities within an HVAC system.
HVAC actuators are used to operate a wide variety of HVAC components such as air dampers, fluid valves, air handling units, and other components that are typically used in HVAC systems. For example, an actuator may be coupled to a valve, or other movable equipment in an HVAC and may be used to drive the equipment (e.g., the valve) between an open position and a closed position. A conventional actuator includes a motor and a drive device (e.g., a hub, a drive train, etc.) that is driven by the motor and coupled to the HVAC component.
The HVAC industry is moving towards the use of control valves capable of maintaining desired water flows regardless of time-varying pressure conditions in the pipes. Some valves are part of a control loop that includes a flow rate sensor that measures the flow rate and sends a signal to a feedback controller. The feedback controller then sends a signal to an actuator to adjust the opening of the valve to achieve the desired flow rate.
The flow rate sensors in the flow control loops have a working range between a minimum and maximum readable flow at which they are configured to provide reliable flow rate measurements. Therefore, flow rates outside of the working range may be unreliable. Accordingly, it would be advantageous to compensate for when the actual flow rate values are below the minimum readable flow corresponding to the flow rate sensor.